Failing weight impact damage characterisation on flax/epoxy laminates

Unidirectional flax/epoxy laminates manufactured using different threads (0.2, 0.9 and 2.3 mm diameter) of untreated flax fibres were tested statically and dynamically (falling weight impact) in a three-point flexural rig. Despite the lower amount of fibres introduced (31% wt. against 55% wt. for both the other laminates), the laminates manufactured using the finest thread did not show lower mechanical properties. This outcome was explained by improved resin impregnation and consequent lower void content, resulting in lower spalling (material loss at rear). Also the study of impact hysteresis curves clarified that a comparable penetration energy is absorbed from the three laminates.